AQUEOUS  EXTRACT  OP  JALAP. 
219 
In  all  these  cases  the  effect  was  due,  in  part,  to  chemical 
action  ;  this,  however,  may  be  excluded. 
11.  A  plate  of  any  refractory  metal,  sufficiently  thin,  and 
with  its  reflective  power  suitably  diminished,  is  raised  to  incan- 
descence in  the  dark  focus.  Gold,  silver,  copper,  aluminium, 
and  platinum  have  been  thus  rendered  incandescent. 
12.  Platinised  platinum  shows  the  effect  best ;  in  a  thin  leaf 
it  may  be  rendered  white-hot,  and  on  it  is  depicted  an  incan- 
descent image  of  the  coal-points.  When  the  points  are  drawn 
apart,  or  caused  to  approach  each  other,  their  incandescent 
images  conform  to  their  motion. 
The  assemblage  of  phenomena  here  described,  and  others  to 
be  referred  to  in  my  complete  memoirs,  may,  I  think,  be  pro- 
perly expressed  by  the  term  "calorescence."  This  word  in- 
volves no  hypothesis,  and  it  harmonises  well  with  the  term 
fluorescence,  now  universally  employed  with  reference  to  the 
more  refrangible  end  of  the  spectrum.* — Chem,  News,  London, 
Feb.  10,  1865. 
ON  THE  AQUEOUS  EXTRACT  OF  JALAP. 
By  Alfred  B.  Taylor. 
"  Does  the  aqueous  extract  prepared  from  Jalap  that  has  been  pre- 
viously exhausted  by  alcohol,  possess  any  medicinal  properties,  or  does 
the  alcoholic  extract  of  jalap  fully  represent  its  virtues?" 
A  superior  quality  of  jalap  was  selected  for  this  experiment. 
It  was  reduced  to  fine  powder,  and  having  been  exhausted  with 
*  On  December  5,  last,  I  tried  the  passage  of  the  rays  from  the  electric 
lamp  through  a  great  number  of  different  colored  glasses.  Incandescence 
was  obtained  through  almost  all  of  them  ;  and  in  one  instance,  the  radia- 
tion passing  through  a  blue  glass,  the  thermograph  of  the  coal  points  was 
of  a  pink  color.  A  thick  black  glass,  obtained  from  Mr.  Ludd,  when  held 
in  front  of  the  lamp,  was  found  to  be  not  perfectly  opaque,  still  the  plati- 
num could  not  be  raised  to  incandescence  at  all  when  placed  in  the  focus. 
Being  called  away  from  the  Royal  -Institution  early  in  the  afternoon,  I 
gave  directions  to  my  assistant,  Mr.  Barrett,  to  continue  the  experiments. 
He  informs  me  that  on  placing  in  the  path  of  the  rays  a  combination  of  two 
thin  plates  of  black  glass,  one  transmitting  a  whitish-green  and  the  other 
a  deep  red,  the  light  was  entirely  intercepted  and  feeble,  though  distinct 
incandescence  was  obtained  at  the  focus.  With  radiation  through  the 
solution  of  iodine,  the  thermograph  on  this  day  rose  to  a  white  heat. 
